4 - Aquatic locomotion Flashcards
Peer
In water there is… gravity and … buoyancy than in air
less
more (leading to increase ability to float)
Freshwater buoyancy
1000kg/m3
Seawater bouyancy
1026kg/m3
Air buoyancy
1.18kg/m3
What is important for reducing friction & turbulence?
The body shape
Forward mvmnt causes?
Frictional drag
Why do invertebrates have higher densities than fresh or marine water?
Due to their constituents - proteins and carbohydrates
- makes them less buoyant
Mechanisms uses to counteract low or maintain neutral buoyancy
- fats (lower density than proteins)
- Ionic solutions (i.e. salts)
- air
Why is the marine copepod Notostomus neutrally buoyant?
Its enlarged carapace contains a low-density body fluid
Why is the deep sea squid Helicocranchia neutrally buoyant?
(is a sluggish swimmer)
has a very large body cavity with fluid that reduces the overall density
What is best for achieving neutral buoyancy?
Air (only 5-7% air volume is needed for an organism to be buoyant in sea- or fresh-water)
Why are air-filled chambers problematic for deep diving?
the hydrostatic pressure associated with increased depth can collapse these chambers
Body types for bouynacy
- Air-filled chambers (Cephalopods)
- Rigid-walled gas chamber (cuttlebone)
How do rigid-walled gas chambers work?
Maintains gas pressure below the externa hydrostatic pressure
Cuttlefish Sepia officinalis attaining neutral buoyancy
- Uses its cuttlebone
- Cuttlebone divided into chambers rigidly supported by lamellae and pillars
The volume of gas in the cuttlebone depends on the ?
- hydrostatic pressure (HP) which forces fluids into the cuttlebone and
- osmotic pressure (OP) that withdraws fluid from the cuttlebone due to differences in solutes between the cuttlebone and blood vessels.
The underlying epithelium regulates… (Cuttlefish)
the osmotic composition of the fluid that partially fills the chambers
Thrust force
‘Force generated by a rotating propeller that enables a vessel to move through the water’
Mechanisms that generate thrust force
- Rowing
- Oscillation
- Undulation
- Jet propulsion
Rowing def
(Diving beetles)
The hydrodynamic drag (fluid resistance) from the rowing movements of the rear legs produce forward thrust during the forward phase of swimming
Oscillation def
A back and forth movement. Creates a ‘flapping’ movement and can be used to generate lift
Undulation def
involves sinusoidal waves passing down the body/a fin/fins. Creates a ‘frilly’ movement that propels the animal forward through the water column.
Sinusoidal waves def
Jet propulsion def
Thrust can be generated by expelling water from different organs or cavities
Jet propulsion creates the movement of the animal in one direction and is achieved by the expulsion of water in the opposite direction, typically from a specialised cavity
Examples of organs or cavities in jet propulsion
- Mantle cavity of a squid
- Rectal chamber of a dragon fly larvae
- Gastrovascular cavity of a jellyfish
- Rapid closing of shells of a bivalve scallop
Jet propulsion mechanism in a cephalopod (3)
- The mantle cavity is first filled with seawater.
- The squid contracts its muscular mantle to send water out of its siphon (jet orifice). The siphon is highly flexible - it can point in any direction and contract independently of the mantle.
- Arrows of “swimming direction” and “Jet direction” are opposite to each other!
Jet orifice def
Why can the siphon point in any direction and contract independently of the mantle?
The siphon is highly flexible
A squid with specialized fins
A squid can oscillate and undulate its lateral fins moving them synchronously or independently, to generate lift and create fine manoeuvres.
What can fin shape and size provide info on? (squid)
- How they are being used
- Where the species lives in the ocean
A mechanically optimal method of swimming with elongated fins has evolved independently at least how many times in both vertebrate and invertebrate swimmers across three different phyla
8 times
Madreproite def & function
special skeletal plate – controls opening to exterior
Stone canal def
Has ring canals and radial canals (one for each arm)
Tiedemann’s bodies def
Coelomocyte production. Part of stone canal
Polian vesicles def
pressure regulators. Part of stone canal
Lateral canal def
ending in tube foot. Consists of ampullae (hydraulic pressure regulator) and podium (hollow, muscular)
Ampulla def
Fluid reservoir used to operate the podium
Lateral canal valve
Isolates tube foot from the rest of the system
Ampulla method
Ampulla contracts – forces fluid into podium – sucker pressed against surface – adhesion with mucus
Podium method
Podium contracts – fluid forced back into ampulla – tube foot released from surface
